Germ-Tracks and Somatic Tracks 89 



matin's clear statements employ the name germ-track. 

 This conception would then correspond exactly to the 

 fertile branches of the cell-pedigree in the illustration 

 selected above. We shall, in the future, keep this shorter 

 designation for it, and in contradistinction we shall call 

 all other sequences of generations of cells, the sterile 

 branches as well as the twigs of our illustration, the 

 somatic tracks. 



A germ-track then, always leads in our cell-pedigree 

 from the fertilized egg-cell to the new egg- or sperm-cell ; 

 we imagine it drawn very straight and clear in our dia- 

 gram. Somatic tracks begin at all points of the germ- 

 tracks and lead, constantly branching, to all the vegeta- 

 tive cells of the body. The cells which are situated on 

 the germ-tracks, can be called germ-track-cells or, accord- 

 ing to Jager, phylogenetic, or perhaps still more distinct- 

 ively, phyletic cells. They are thus sufficiently distin- 

 guished from the ontogenetic or somatic cells. 



It is a matter of course that the distinctions intro- 

 duced here, and therefore also the names and their defi- 

 nitions, are of a purely descriptive nature. There can be 

 no question as to their correctness since they are quite 

 arbitrary. The question is only, are they practical, i. e., 

 can they lead us to a clear insight. 



We must not wish to substitute a theoretical meaning 

 for the conception of the germ-tracks. Otherwise the 

 definition would not be sufficiently clear. Therefore 

 Weismann's germ-cells correspond only in their main 

 features, and not everywhere, with our germ-track cells. 

 This is especially shown by the circumstance that, ac- 

 cording to his theory, sexual cells are frequently produced 

 by somatic cells, and that he devotes a detailed discussion 

 to the fact that the splitting off occurs a little sooner in 



